By virtue of the progress in information communication networks and the like such as the Internet in these few years, each user can now easily access network information through individual-oriented terminals employing a cellular phone or the like.
In such information communication, information is transmitted through digital signals. It is now possible to obtain copied music and video information transmitted via the aforementioned information communication network without degradation in the audio quality and picture quality of the copy data, even in the case where the copy operation is performed by an individual user.
Thus, there is a possibility of the copyright of the copyright owner being significantly infringed unless some appropriate measures to protect copyrights are taken when any content data subject to copyright protection such as music and image information is to be transmitted on the information communication network.
However, if copyright protection is given top priority so that distribution of content data through the disseminating digital information communication network is suppressed, the copyright owner who can essentially collect a predetermined copyright royalty for copies of a copyrighted work will also incur some disbenefit.
In the case where content data such as music data is distributed through a digital information communication network as described above, each user will record the distributed data onto some recording apparatus, and then reproduce the data using a reproduction apparatus.
Such recording apparatuses include, for example, a medium that can have data written and erased electrically such as a memory card.
As the apparatus to reproduce distributed music data, the cellular phone per se used to receive such data distribution can be employed, or when the recording apparatus such as a memory card is detachable from the apparatus that receives distribution, a dedicated reproduction apparatus can be used.
In the case where distribution of content data such as music data is to be received through a digital information communication network, particularly through a radio communication network, the communication may be cut off before the music data is completely distributed depending upon the state of the communication line. In the case where encrypted content data which is an encrypted version of content data is decrypted and reproduction information required for reproduction is to be distributed, any disruption in communication during distribution of the encrypted content data can be mended by establishing connection again and continuing data reception. Since the accounting process towards the user is carried out simultaneously in distributing reproduction information, the user will request retransmission of the reproduction information after connection is established again with respect to such disrupted communication. However, reproduction information should not be retransmitted incautiously in response to a request from the standpoint of protecting the rights of copyright owners. However, if retransmission is not conducted, the user will not be able to obtain the reproduction information even though the accounting process has been effected.